This invention relates generally to apparatus having a data transducer (head) or transducers for reading and/or writing data on disk-like record media typically including magnetic disks. More particularly, this invention pertains to a rotating disk data storage apparatus built on what is known in the art as Winchester technology, such that the transducers "fly" or are airborne at a small spacing from the data storage surfaces of a hard disk during the transfer of data therewith. Still more particularly, the invention deals with a mechanism incorporated in such an apparatus for lessening load forces exerted by the transducers on the disk as the transducers slide over the disk surfaces during the starting or ending period of disk rotation.
In flying transducer data storage systems, as is well known, a hard disk or disks are employed which have a magnetic data storage medium coated or otherwise formed on the major surfaces thereof. A series of concentric data storage tracks are formed on each disk surface. Disk diameters in consideration here are two and a half inches or three and a half inches, although various other diameter disks are used in practice.
For reading or writing data on the storage surface of the disk, data transducers are gimbaled on the distal ends of resilient transducer carrier beams which may be cantilevered directly to a voice coil motor or may be coupled to any equivalent transducer positioning means. The voice coil motor operates to move the transducers across the data tracks and to position them on any desired tracks.
Normally, that is, when the disk is out of rotation, the transducers are held in contact with predefined landing zones on the disk surfaces, which zones may be either radially inside or outside the data storage tracks, under the bias of the transducer carrier beams and the gimbal springs. The transducers slide over the disk surfaces when the disk is set into rotation. Then, as the disk picks up speed, the transducers ride upon an air cushion created by disk rotation and start flying over the disk surfaces for reading or writing data thereon.
The construction and operation of the data storage apparatus described hereinbefore is based upon the contact start stop scheme. This scheme, as so far practiced in the art, has given rise to several inconveniences. One of these is the rapid, uneven wear of the disk as the transducers slide over the landing zone at the start and end of each run of disk rotation. The particles produced by disk abrasion have also adversely affected the various working parts of apparatus.
Another inconvenience is the large starting current requirement of the disk drive motor, due of course to the great starting torque imposed by the transducers sliding over the disk surfaces under the forces of both transducer carrier beams and gimbal springs. This large starting current requirement has presented a particularly serious problem when the apparatus is battery operated, because of the shorter useful life of the battery.
Additionally, with the repeated start and stop of disk rotation, the transducers have been easy to grind the disk surfaces to such smoothness as to result in a substantial increase in frictional resistance. The starting current requirement of the disk drive motor has further increased with the increase in frictional resistance. This same reason has also given rise to the danger of the transducers sticking to the disk surfaces so fast as to be ruined by the forced starting of disk rotation.
An obvious remedy to the listed difficulties arising from the contact start stop method might be to hold the transducers out of contact with the disk surfaces against the spring forces during the starting and ending periods of disk rotation. Various suggestions have actually been made for this noncontact start stop method. Although the known noncontact methods are free from the difficulties of the contact start stop scheme, they have their own drawbacks.
According to one such known noncontact method, the transducers are held spaced approximately one to two millimeters from the disk surfaces during the starting period. Then, as the disk picks up speed to the normal value, the transducers must be allowed to fly upon an air cushion created by disk rotation, with the standard spacing of 0.4 micrometers. Great difficulties have been involved in controlling this transition of the transducer spacings. Furthermore, as this noncontact starting of the disk is repeated in use of the disk drive, the danger has arisen of the transducers being destroyed by coming into contact with the disk.